1. Field of the Invention
The present invention relates to substrate processing apparatus for and substrate processing method of supplying a treatment liquid onto the surface of a substrate to treat the same, and more particularly to substrate processing apparatus and method to be applied to a process in which a treatment liquid is contaminated by metal. Examples of a substrate to be treated, include a semiconductor wafer, a liquid-crystal-display-device glass substrate, a plasma-display glass substrate and the like.
2. Description of Related Art
Higher-density integration and faster operation of semiconductor integrated circuit elements are the requirements of the marketplace. To meet such requirements, copper wirings lower in resistance are increasingly used instead of conventional aluminium wirings. When a copper wiring is combined with a low-permittivity insulating film (a so-called Low-k film or insulating film made of material of which relative permittivity is smaller than that of silicon oxide) to form a multi-layer wiring, this achieves an integrated circuit element operable at a very high speed.
Copper wirings at different layers are connected to each other through a copper plug embedded in a via formed in the interlaminar insulating film. To form a fine wiring pattern, a via having a high aspect ratio is required. To form such a via, there is applied a dry etching method represented by a reactive ion etching.
According to the dry etching, however, not only the film to be treated but also a resist are corroded. A part of the resist is then changed in quality and remains, as a polymer (resist residue), on the substrate surface. Because the wiring pattern is fine, the polymer must securely be removed from the substrate before the subsequent step.
Polymer removal is carried out by supplying a polymer removing liquid onto the substrate to selectively etch the polymer.
The polymer contains copper scattered during the dry etching step. The copper is dissolved as copper ions in the polymer removing liquid. Accordingly, the polymer removing liquid after used for substrate treatment is thrown away at the present time.
However, the polymer removing liquid comprises an organic solvent mixture having a complicated composition and is therefore expensive. Accordingly, to reduce the production cost of semiconductor devices and the like, it is worth considering that the polymer removing liquid is not thrown away after single-use, but the used polymer removing liquid is collected and reutilized.
However, while the polymer removing liquid is repeatedly collected and reutilized, copper ions are accumulated in the polymer removing liquid, causing the same to be a metal contamination source. More specifically, copper ions are attached to the reverse side of a substrate or to other portions (oxide film surface and the like) of the substrate surface than the copper thin film. Such copper ions contaminate other substrate processing apparatus to which the substrate has been transferred for other treatment. This results in contamination of other substrates. As a result, there is a risk of having a profound effect on the characteristics of semiconductor devices or the like.
Similar problems may be expected not only in the polymer removing treatment, but also in a treatment in which metal contamination is accumulated in a treatment liquid, such as a bevel etching treatment for selectively removing a copper thin film at the peripheral edge of the surface of a semiconductor wafer, a reverse-side etching treatment for removing the metal contamination at the reverse side of a semiconductor wafer, or the like.